1. Field of the Invention
The present invention relates to a liquid distributor to be used in a substance and/or heat exchanging tower. The liquid distributor is a device which is used in a tower in which a counter-flow of a liquid and a gas is effected and thereby the liquid and the gas come into contact with each other, and which is used for uniformly distributing a liquid onto a structure packed in the inside of the tower, a so-called packing.
2. Prior Art
There are many kinds of liquid distributors conventionally used in a substance and/or heat exchanging tower which vary in their methods of distribution. One conventional distributor comprises a plurality of liquid distributing tubes placed in parallel along the lateral axis of a tower, the distributing tubes having opening nozzle holes at intervals along the lower part thereof. In the distributing tube of this type, the liquid falls on the packing from the nozzle holes and the liquid is distributed onto the packing at the position of the nozzle holes. The distributing tubes are connected to a main tube provided also in parallel to the lateral axis of the tower, and the main tube is connected to a longitudinal tube provided in parallel to the longitudinal axis of the tower. The amount of liquid flowing from the nozzle holes depends on the head of liquid accumulating in the longitudinal tube, the diameter of the nozzle and the number of nozzles. Among these parameters, it is the head that changes when the distributor is used. The flow of the liquid changes depending on the change in the head. When the head is high, a flow velocity increases; on the other hand, when the head is low, a flow velocity is reduced. Due to this change in flow velocity, nozzle holes are generally opened in a vertically downward direction on the distributing tube so that the direction of a flow and the distributing position do not change. If the diameter of a nozzle and the number of nozzles are determined on the basis of the case of a large amount of flow, the liquid readily flows out from the nozzle holes near the longitudinal tube when the amount of flow is small, and thereby it becomes difficult to distribute the liquid uniformly.
The amount of a liquid to be distributed in a substance and/or heat exchanging tower varies according to the operation conditions of the tower. When the amount of liquid to be distributed increases or decreases largely at the time of an operation, such a distributor as mentioned above which is provided nozzle holes at intervals on the lower part thereof is not effective.
Another type of distributor is a so-called overflow type which comprises distributing tubes formed in a U-shaped trough. In this type of distributor, a liquid to be distributed is overflowed from a notch of the upper end of the U-shaped trough; such a distributor however occupies a larger area of the tower due to its construction, which may cause pressure loss of a rising gas at the time of operation.
There is another type of distributor which comprises guide pins provided on the notches guiding a liquid downwardly under capillary action and letting the liquid fall from the lower end of the pin, to accomplish uniform liquid distribution. However the cost thereof is very high. In a distributor of this kind, in order to effect uniform overflow of a liquid, it is necessary for the upper end surface of the distributor to be kept horizontal. This results in difficulties in its provision in a tower.
Moreover, in such a type of distributor, it is also necessary to prevent waves from occurring in the surface of a liquid so as to enable uniform overflow of the liquid. However, it is technically difficult to remove waves. When an amount of a liquid to be distributed is large and a flow velocity is high, it is difficult to prevent waves from occurring.
As another method there is known a method according to Japanese Patent Application No. 45991/1988 (corresponding to Japanese Patent Publication (Kokai) No. 63-243689), which comprises providing openings in the side-wall of a distributing tube formed in a U-shaped trough, letting a liquid flow out from the openings, strike a guide wall and spread as a result. According to this method, however, a considerable velocity must be imparted to the outflowing liquid, and hence the method is not applicable to slow flowing liquids.